The invention relates generally to torsion oscillators, also termed resonant galvanometers, as well as to bidirectional scanning and imaging apparatuses including such torsion oscillators, and, more particularly, to systems for driving torsion oscillators.
Torsion oscillators which include an oscillating mirror may be employed in bidirectional scanning and imaging devices, such as laser printers, as an alternative to a rotating polygonal mirror.
As disclosed in Klement U.S. patent application Ser. No. 10/093,754, filed Mar. 8, 2002, and published as No. US 2003/0169055 A1 on Sep. 11, 2003, titled “Torsion Oscillator Stabilization,” a torsion oscillator having an oscillating mirrored surface may be employed as a laser scanner when a laser is directed at the oscillating mirrored surface. A scan path which corresponds to motion of the oscillating mirror is thereby defined. The mirror angle changes sinusoidally with respect to time at a certain amount of sweep or scan angle (termed amplitude), at a certain repetition rate (termed frequency) and with a potential lack of symmetry with respect to the using apparatus (termed median offset or simply offset). Amplitude, frequency and offset are stabilized and controlled for useful operation, employing feedback from sensors which sense the light beam at predetermined positions in the scan path. More particularly, amplitude, frequency and offset are controlled such that the time interval during which the scanned beam traverses an imaging window is kept constant, and the offset is kept constant.